Do you want to add any other resort on to your ski big 3 trip?
Kicking Horse is 45-60 minutes west of Lake Louise. It has better snow than Banff and it is known for it's inbounds chutes and steeps. The lift system is pretty limited and you'll need to hike a bit (in-bounds) to get the most of your day, but Kicking Horse skis well in March. It's my favorite resort in the region.
Down south there is castle near Pincher Creek, Alberta. Castle has great fall line runs...and high winds. The wind transport at castle is seriously fun. The lift infrastructure here is very old...the main upper lift is a retired double chair from sunshine, but midweek you can get a lot of laps in. Just go after the wind, not during a wind storm! Castle skis best mid February to mid March. Castle isn't close to banff (3.5 hour drive), but would be on your way if you flew into kallispell.
Fernie is 1.5 hours west of Castle. It gets the most snow in the region and has excellent tree skiing. I have had some of my best powder days of my life at Fernie. Unfortunately, the resort is pretty low in elevation (the top of the "old side" is barely higher than the base of lake louise), so it can get mid-winter rain. It's one of my favorite hills, but timing is everything. I wouldn't commit to Fernie too far in advance. It's easy to get a midweek room anyway. Unfortunately, the best time to visit Fernie tends to be earlier in the seasaon (January and February), but March can be good if you time it right.
I wouldn't make a point of skiing Panorama, Nakiska, or Kimberly.
Marmot Basin in Jasper is okay...not as good as Louise, Sunshine, Fernie, Kicking Horse, or Castle, but the drive to Jasper might make skiing worth it. The drive is spectacular.
Red, Whitewater, and Revelstoke are all worth visiting, but you are starting to get further from the calgary/banff base with these options, especially Red and Whitewater.
Revelstoke is on IKON, so it is probably worth tagging? How much driving do you want to do?